<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>margin负值的巧妙运用</title>
    <style>
      ul li {
        position: relative;
        float: left;
        list-style: none;
        width: 150px;
        height: 200px;
        border: 1px solid red;
        margin-left: -1px;
      }

      /* ul li:hover {
        情况1. 如果盒子没有定位，则鼠标经过添加相对定位即可
        position: relative;
        border: 1px solid blue;

       } */
      ul li:hover {
        /* 情况2.如果li都有定位，则利用 z-index 提高层级 */
        z-index: 1;
        border: 1px solid blue;
      }
    </style>
  </head>

  <body>
    <ul>
      <li>1</li>
      <li>2</li>
      <li>3</li>
      <li>4</li>
      <li>5</li>
    </ul>
  </body>
</html>
